Fv B> 16 17 18 19 20 21 22 24 26 28
28 1.75 1.65 1.56 1.47 1.40 1.33 1.27 1.17 1.08 1.00
29 1.81 1.71 1.61 1.53 1.45 1.38 1.32 1.21 1.12 1.04
30 1.88 1.76 1.67 1.58 1.50 1.43 1.36 1.25 1.15 1.07
31 1.94 1.82 1.72 1.63 1.55 1.48 1.41 1.29 1.19 1.11
32 2.00 1.88 1.78 1.68 1.60 1.52 1.45 1.33 1.23 1.14
33 2.06 1.94 1.83 1.74 1.65 1.57 1.50 1.38 1.27 1.18
34 2.13 2.00 1.89 1.79 1.70 1.62 1.55 1.42 1.31 1.21
35 2.19 2.06 1.94 1.84 1.75 1.67 1.59 1.46 1.35 1.25
36 2.25 2.12 2.00 1.89 1.80 1.71 1.64 1.50 1.38 1.29
37 2.31 2.18 2.06 1.95 1.85 1.76 1.68 1.54 1.42 1.32
38 2.38 2.24 2.11 2.00 1.90 1.81 1.73 1.58 1.46 1.36
39 2.44 2.29 2.17 2.05 1.95 1.86 1.77 1.63 1.50 1.39
40 2.50 2.35 2.22 2.11 2.00 1.90 1.82 1.67 1.54 1.43
41 2.56 2.41 2.28 2.16 2.05 1.95 1.86 1.71 1.58 1.46
42 2.63 2.47 2.33 2.21 2.10 2.00 1.91 1.75 1.62 1.50
43 2.69 2.53 2.39 2.26 2.15 2.05 1.95 1.79 1.65 1.54
44 2.75 2.59 2.44 2.32 2.20 2.10 2.00 1.83 1.69 1.57
45 2.81 2.65 2.50 2.37 2.25 2.14 2.05 1.88 1.73 1.61
46 2.88 2.71 2.56 2.42 2.30 2.19 2.09 1.92 1.77 1.64
47 2.94 2.76 2.61 2.47 2.35 2.24 2.14 1.96 1.81 1.68
48 3.00 2.82 2.67 2.53 2.40 2.29 2.18 2.00 1.85 1.71
49 3.06 2.88 2.72 2.58 2.45 2.33 2.23 2.04 1.88 1.75
50 3.13 2.94 2.78 2.63 2.50 2.38 2.27 2.08 1.92 1.79
51 3.19 3.00 2.83 2.68 2.55 2.43 2.32 2.13 1.96 1.82
52 3.25 3.06 2.89 2.74 2.60 2.48 2.36 2.17 2.00 1.86

What do the figures mean? Well, for a single turn of the cranks the wheel turns x times. X varies depending on the no. of teeth on your chainring and freewheel. Find your teeth (no not those teeth) in the table headings to find X.
The figures in bold represent the combinations I have seen. However an 18 tooth rear is by far the most common. The blue ones are what I use. Remember that there is no right or wrong - use what works for you.
Note these figures do not consider crank length or tyre size. If you are comparing bikes with different tyre sizes, multiply the figures by the wheel circumference.

Andy Mittell Practicing